10-8
Testing and Troubleshooting
Date Code 20020129
SEL-387E Instruction Manual
Metering
Current Metering
Step 1.
Purpose: Connect simulated power system secondary current sources to the relay.
Method: Turn relay power off and connect current sources. If three current sources
are available, connect them to the relay in a full three-phase connection,
as shown in Figure 10.3. If only two current sources are available,
connect the sources as shown in Figure 10.4 to generate balanced
positive-sequence currents:
a. Connect the A-phase and B-phase current sources to the dotted A and
B current input terminals.
b. Connect both undotted A and B current input terminals to the undotted
C current input terminal.
c. Connect the dotted C current input terminal to both the A and B
current source returns.
Set the current sources to deliver one ampere with A-phase at 0 degrees,
B-phase lagging A-phase by 120 degrees, and C-phase leading A phase by
120 degrees.
Step 2.
Purpose: Verify correct current levels.
Method: Turn relay power on, and use the
METER
command to measure the
currents applied in Step 1. With applied currents of one ampere per phase
and a current transformer ratio of 120:1 (
SHO CTR1 <ENTER>
displays
the CT ratios for each winding,
<CTRL> X
cancels scrolling), the
displayed line currents should be the applied current, 120 amperes ±3%,
±12 amperes.
Step 3.
Purpose: Verify phase rotation.
Method: Verify that residual (IR) and negative-sequence (3I2) quantities are
approximately zero. If IR equals three times the applied current, then all
three phases have the same angle. If 3I2 equals three times the applied
current, then the phase rotation is reversed. Turn the current sources off.